title: IGF-I/PI3K/Akt and IGF-I/MAPK/ERK pathways in vivo in skeletal muscle are regulated by nutrition and contribute to somatic growth in the fine flounder.
abstract: The insulin-like growth factor-I (IGF-I) is a key regulator of skeletal muscle growth in vertebrates, promoting mitogenic and anabolic effects through the activation of the MAPK/ERK and the PI3K/Akt signaling pathways. Nutrition also affects skeletal muscle growth, activating intracellular pathways and inducing protein synthesis and accretion. Thus, both hormonal and nutritional signaling regulate muscle mass. In this context, plasma IGF-I levels and the activation of both pathways in response to food were evaluated in the fine flounder using fasting and refeeding trials. The present study describes for the first time in a nonmammalian species that the MAPK/ERK and PI3K/Akt are activated by exogenous circulating IGF-I, as well as showing that the MAPK/ERK pathway activation is modulated by the nutritional status. Also, these results show that there is a time-dependent regulation of IGF-I plasma levels and its signaling pathways in muscle. Together, these results suggest that the nutritionally managed IGF-I could be regulating the activation of the MAPK/ERK and the PI3K/Akt signaling pathways differentially according to the nutritional status, triggering different effects in growth parameters and therefore contributing to somatic growth in fish. This study contributes to the understanding of the nutrient regulation of IGF-I and its signaling pathways in skeletal muscle growth in nonmammalian species, therefore providing insight concerning the events controlling somatic growth in vertebrates.
authors.affiliation: Laboratorio de Biotecnología Molecular, Facultad de Ciencias Biológicas, Universidad Andres Bello, Santiago, Chile.
authors.forename: Eduardo N
authors.initials: EN
authors.lastname: Fuentes
authors.forename: Björn Thrandur
authors.initials: BT
authors.lastname: Björnsson
authors.forename: Juan Antonio
authors.initials: JA
authors.lastname: Valdés
authors.forename: Ingibjörg Eir
authors.initials: IE
authors.lastname: Einarsdottir
authors.forename: Belen
authors.initials: B
authors.lastname: Lorca
authors.forename: Marco
authors.initials: M
authors.lastname: Alvarez
authors.forename: Alfredo
authors.initials: A
authors.lastname: Molina
mesh_terms: D000818:Animals; D004435:Eating / Q000502:physiology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000502:physiology*; D005215:Fasting / Q000502:physiology; D005432:Flounder / Q000254:growth & development* / Q000502:physiology*; D007334:Insulin-Like Growth Factor I / Q000502:physiology*; D020929:Mitogen-Activated Protein Kinase Kinases / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D009752:Nutritional Status / Q000502:physiology*; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology*; D051057:Proto-Oncogene Proteins c-akt / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology; D013997:Time Factors
chemical_list: D007334:Insulin-Like Growth Factor I; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D048049:Extracellular Signal-Regulated MAP Kinases; D020929:Mitogen-Activated Protein Kinase Kinases